JP2568284B2 - Automatic operation method of air liquefaction separation device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to air used in a steel mill to produce product oxygen (O ₂ ), product nitrogen (N ₂ ), waste nitrogen, argon (Ar), etc. In a separation and liquefaction device (hereinafter also referred to as an oxygen plant), air that is automatically increased / decreased to obtain a target generation amount input by an operator, depending on plant conditions, that is, oxygen purity, nitrogen purity, current generation amount, etc. The present invention relates to a method of operating a separation / liquefaction device.

[Conventional technology]

FIG. 5 is a block diagram showing an outline of an oxygen plant.

That is, the air as a raw material is passed through an air filter, compressed into about 5 kg / cm ² by an air compressor, and then cooled and washed in a washing and cooling tower. Next, it enters a heat exchanger and exchanges heat with product oxygen, product nitrogen, and waste nitrogen, is cooled to about -170 ° C, and is guided to the lower column of the rectification column. The air introduced into the lower tower is preliminarily rectified to obtain nitrogen gas rich in nitrogen at the top of the lower tower and becomes liquid air having an oxygen content of about 40% at the bottom of the lower tower. The gaseous air extracted from the middle part of the lower tower enters a post-expansion turbine used for heat exchange with the raw material air in the heat exchanger, where cold is generated and then guided to the upper tower. On the other hand, liquid air accumulated at the bottom of the lower tower and liquid nitrogen containing a large amount of nitrogen accumulated at the top and the vicinity of the top are introduced into the middle, upper and vicinity of the upper tower respectively through conduits. Further, it is rectified and separated in the upper tower, and is extracted as product oxygen gas from the bottom of the upper tower, product nitrogen gas from the top, and waste nitrogen gas from the middle. After heat exchange with the raw material air in the heat exchanger as described above, it is discharged to the outside. Supplied. On the other hand, the raw material argon gas is extracted from the vicinity of the middle part of the upper tower and supplied to the crude argon tower through a conduit.

Conventionally, in the operation of increasing or decreasing the generation amount in such an oxygen plant, it is general that an operator judges a lot of process data and manually operates it, but recently, an example of introducing a computer and automating it is also available. is there.

[Problems to be Solved by the Invention]

However, both methods have the following problems.

In the case of operation by an operator (human) (1) Even if it is a skilled person, it is necessary to make a judgment based on a lot of information because it is a manual operation, and it is easy for an erroneous operation to occur, and the oxygen plant itself has a large time constant. It takes a long time to hold. Therefore, the mental of the operator,
Physical burden increases.

(2) When the purity or the like is deteriorated due to an erroneous operation, the oxygen plant itself has a large time constant, so that it takes a long time to recover and stabilize the purity, which hinders stable supply to each user.

(3) Since changing the oxygen production amount requires skilled and time-consuming work, it is difficult to accurately follow the change in the amount used.

(4) In consideration of the fact that the supply destination should not hinder the operation due to the shortage of the supply amount, the production is performed more than is actually required at the use destination. The surplus is used as it is and is diffused, so there is much waste.

(5) Since there is a tendency to perform an operation with an allowance in order to avoid the purity or more due to the change in the amount of generation, there is a waste of dissipating it unused.

(6) It is difficult for a relatively inexperienced operator to expect sufficient skilled operation.

(7) Even a skilled operator has individual differences.

In the case of automatic operation by computer (1) It is limited to the increase / decrease operation related to only product oxygen or only argon obtained in the oxygen plant, and other product nitrogen cannot be increased / decreased at the same time in the opposite direction.

Therefore, the problems of the present invention are (1) standardization and omission of work by automation (2) prevention of loss such as emission when surplus occurs (3) cost reduction by optimal operation (4) prevention of erroneous operation (5) operator In order to solve the above problems, in the automatic operation method of the air liquefaction separation device according to the present invention, oxygen is used as a raw material to produce oxygen, nitrogen and the like as products, In the air liquefaction separation device to be supplied to the demand side, when the liquefaction separation device is automatically operated in response to the irregular fluctuations in the production amount of the product required from the demand side, the demand side specifies When there is an irregular increase / decrease request for the production amount of a product, it is judged whether it is possible to meet the request from the current operating condition of the air liquefaction separation device. Based on the operating experience of the air liquefaction separation device, the variable of the antecedent part (if part) is whether or not the raw material supply amount is appropriate in relation to the increase / decrease amount of product manufacturing requested from the demand side. And a first knowledge base consisting of an inference rule which is set as a variable of a consequent part (then part) by selecting an operation end related to raw material supply corresponding to it, and an operation amount of the selected operation end. Based on the operation experience of the liquefaction separation device, the data of the product quality abnormality that may occur during the operation of the liquefaction separation device is used as the variable of the antecedent part (if part), and the adjustment operation for the quality recovery to cope with it is taken. A second knowledge base consisting of inference rules set as variables of the consequent part (then part) is to be provided.

[Operation] When it is determined in the increase / decrease operation propriety determination table that the increase / decrease operation is possible, the raw material supply amount is appropriate in relation to the requested increase / decrease amount by referring to the first knowledge base. If the product quality abnormality is detected during the operation of the air liquefaction separation device, the optimum operation end and its operation amount corresponding to whether or not the operation end is determined and executed. By referring to the knowledge base of No. 2, the adjustment operation for recovering the quality abnormality is determined and executed.

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing an increase / decrease operation propriety determination table, and FIG. 3 is a graph for explaining a raw material air amount accompanying a change in product oxygen generation amount, FIG. 4 is a graph for explaining the valve opening degree of the reflux liquid control valve corresponding to the change of the raw material air amount.

In FIG. 1, 1 is a computer system, 2 is a measurement control device, 3 is an oxygen plant, 4 is a CRT, and 5 is a printer. That is, the computer system 1 for operating the oxygen plant 3 controlled via the measurement control device 2 has a man-machine interface 11, an increase / decrease operation availability determination table 12, a constant file 13, an expert system 14, an input processing unit 15, and a control. The expert system is composed of the output unit 16 and so on, and the expert system has an inference mechanism and the know-how and procedure for operating the oxygen plant, which states "if the state of if data".
Rule format of "then operation" and "if data state" or "then
The concrete contents of "operation" are composed of a knowledge base expressed by a mathematical expression such as a comparison logical expression or four arithmetic operations. In other words, the value obtained by the inference mechanism, that is, the rule in which the "state of the if data" matches, is searched from the knowledge base,
The optimum operation end and operation amount defined in “then operation” are transmitted to the measurement control device, and at the same time, the operator is notified of the value and operation amount obtained by inference every time inference is performed. , The expert system 14 related to the increase / decrease operation is printed on the form. The operator must input any one of the product oxygen, product nitrogen, and crude argon generation amounts from the operation monitoring screen 4 or a plurality of emission amount instruction values at the same time. The current flow rate (amount of raw material air, amount of product oxygen, amount of product nitrogen, amount of crude argon), purity (product oxygen purity, product nitrogen purity, oxygen concentration in crude argon), liquid oxygen level at the top of the upper column (Level), process data such as the valve opening of the valve that regulates the flow rate of liquid nitrogen (reflux liquid) from the lower tower to the upper tower, and as described above in the rule format of "if data state then operation" In the created knowledge base, a rule matching the “state of if data” is searched from the knowledge base, and the increase / decrease operation is performed while changing the setting of the operation end and the operation amount defined in the “then operation”. The outline procedure is as follows.

The operator uses the operation monitoring screen 4 to input any one of product oxygen, product nitrogen, and crude argon generation amount setting values (others maintain the current generation amount) or a plurality of values at the same time.

It is judged whether or not there is an error in this input value (exceeding the upper and lower limits of the amount generated during steady operation), and if there is an error in the set value, the operator is notified of that fact and re-input. Encourage. If there is no mistake in the set value, it is compared with the current amount of product oxygen, product nitrogen, and crude argon generated, and if the newly entered set value is larger, it is an increase operation, and if the set value is smaller, it is a decrease operation. Each operation item (operation pattern) is automatically determined, and the process proceeds to the next.

Current plant status (product oxygen purity, product nitrogen purity,
Whether the specified operation (operation item) is possible or not with respect to the oxygen concentration in crude argon and the liquid oxygen level are in the improvement tendency, the deterioration tendency, or the stable region) is shown in FIG. To determine. For example, in the case of a single oxygen increase operation (an operation to increase only the current product oxygen generation amount and maintain the other product nitrogen generation amount and crude argon generation amount as it is), the product oxygen purity is stable (managed as product quality). Oxygen in the product oxygen during the time course within the purity controlled as product quality. If the concentration is high (that is, the concentration is improving in the 100% direction), then check the increase / decrease operation permission / prohibition determination table in FIG. ₂ for “improvement of O ₂ purity (%)” and Since the judgment in the column where "O ₂ increase" intersects is "OK", it is judged that the oxygen increase single operation is possible for the current product oxygen purity. Further, the product nitrogen purity, the oxygen concentration in crude argon, and the liquid oxygen level are also compared with the increase / decrease operation permission / inhibition determination table of FIG. 2 and the same determination is performed, and if all conditions are satisfied (acceptable), the operation is performed. In this case, the oxygen increasing single operation is accepted.

As a result of the determination, if even one (no) of the increase / decrease operation availability determination table of FIG. 2 is collated, it is determined that the specified operation cannot be performed (no) in the current plant status, and the operator is notified of that fact. Cancel the specified operation. On the other hand, even if "No" in the increase / decrease operation permission / inhibition determination table of FIG. 2 is not collated and all are "OK", and it is determined that the designated operation is possible (OK), the process proceeds to the next step. Further, the contents of the increase / decrease operation permission / inhibition determination table 12 can be changed interactively from the same CRT by switching the operation monitoring screen 4.

It is determined whether or not the amount of raw material air corresponds to the change in the amount of one step of the product generation amount (unit operation amount to change the setting in one operation). That is, the current amount of raw material air (Air amount) corresponds to the change in product generation amount by 1 step amount.
Whether or not is determined by using the “state of if data” of rule 1 or rule 2 to be described later. If the rule 2 "if Air amount is not required air amount" is matched,
In that case, follow the rule 2 "Increase the amount of then air by 1 step" to adjust the amount of raw material air accordingly. In other words, in Rule 2 “Increase the amount of then Air by 1 step”,
For example, the amount of change in the raw material air amount (= ΔO ₂
The value obtained by adding C) is passed to the measurement control device via the control output unit as the amount of raw material air corresponding to one step change of the product oxygen generation amount. On the other hand, in Rule 1, “if Air amount is required Ai
If the “amount of r air” is collated and matched, in that case, the amount of raw material air is maintained according to Rule 1 “The amount of then air is maintained as is”. An example of the knowledge base in this case is as follows.

Rule 1: Rule to judge that the amount of air is the current status IF Air amount is the necessary amount of air THEN The amount of air is to maintain the current status Rule 2: Rule to judge that the amount of air is increased by 1 step IF Air amount is not the necessary amount of air THEN Increase the amount of air by 1 step Note that the judgment formula for determining "if air amount is the required air amount" in rule 1 and "if air amount is not the required air amount" in rule 2, for example, product The raw material air amount corresponding to the one step change of the oxygen generation amount is calculated by the following formula. For example, the rule 1 "if air amount is the required air amount" is satisfied if the value of F _Air ′ calculated by the following formula is compared with the current raw material air amount and the raw material air amount is larger. Be true. On the other hand, the rule 2, "an if Air amount is not an Air volume required" is 'compares the values and the current feed air quantity, F _Air' F _Air becomes true satisfied if is larger value of . In addition, whether or not to use this mathematical formula can be arbitrarily changed when creating the rule.

F _Air ′ = F _Air ＋ C · ΔO ₂ F _Air ′: Raw material air amount (absolute value) corresponding to 1 step change of product oxygen generation amount F _Air : Theoretical raw material air amount (Air / O ₂ ratio) ΔO ₂ : Change amount of one step of product oxygen generation amount C: Constant ΔAir: Air amount change amount (= C · ΔO ₂ ). The above relationship is shown in FIG. These mathematical expressions are also stored in the knowledge base, and the contents of ΔO ₂ , C, etc. can be changed interactively from the same CRT by switching the operation monitoring screen 4.

At the same time, the valve opening of the reflux liquid control valve corresponding to the change of the raw material air amount is calculated. That is, the range of product oxygen generation amount (O ₂ amount) as shown in FIG. 4 and the raw material air amount (Air
Amount), product oxygen generation amount (O ₂ amount), product nitrogen generation amount (N
₂ ) and constants K11 to K13, K21 to k23, k31 to K33, the valve opening is calculated from the following formula. Whether or not this mathematical expression is used can be arbitrarily changed when creating the rule. Further, K11 to K13 are in the range (I) and K21 to K23 are in the range (I).
I) and K31 to K33 are constants for each amount in the range (III).

Valve opening = K11 * Air volume + K12 * O ₂ amount + K13 * N ₂ + amount constant valve opening = K21 * Air volume + K22 * O ₂ amount + K23 * N ₂ + amount constant valve opening = K31 * Air volume + K32 * O ₂ amount + K33 * N ₂ + amount constant even these equations are stored in the knowledge base, constant K11~K13, K21~K23, by the like K31~K33 switching the operation monitoring screen 4, the same The contents can be changed interactively on the CRT.

At the same time, the product quantity is changed by one step. For example, in the case of the product oxygen generation amount, "Increase the amount of then O ₂ by 1 step" will change the product oxygen generation amount from the current product oxygen generation amount.
The value obtained by adding the 1step change amount (ΔO ₂ ) is passed to the measurement control device via the control output unit as the new product oxygen generation amount. This operation is also described by the rules and mathematical formulas described above.

When the target generation amount instruction value is reached, the process is completed and the operator is notified of that. If the target value is not reached, wait for N minutes and perform the above operations 1). The standby time (N minutes) can also be changed interactively from the same CRT by switching the operation monitoring screen 4.

On the other hand, the expert system 14 related to adjustment operation
If a program that constantly monitors the plant status detects a purity abnormality (out of the purity management area managed as product quality), first, if the increase / decrease operation is in progress,
The determination is made using the increase / decrease operation availability determination table as shown in FIG. For example, when the oxygen increase single operation (the operation to increase only the current product oxygen generation amount and to maintain the other product nitrogen generation amount and crude argon generation amount as it is) is being performed, the product oxygen purity is improved (product Oxygen concentration in oxygen tends to increase, and product nitrogen purity improves (oxygen concentration in product nitrogen ppmO
₍₂ becomes low) and other monitoring items show no abnormality, the “O ₂ purity (%) improvement” and “O ₂ increase” are checked by collating with the increase / decrease operation availability determination table in FIG. 2. The column where "" intersects is judged as "OK", and the column where "N ₂ purity (ppmO ₂ ) is improved" and "O ₂ increase" is judged as "OK". For product nitrogen purity improvement (too good) tendency, only monitoring is performed without performing purity recovery operation (adjustment operation), and increase / decrease operation is continued without interruption To determine. if,
As a result of the determination, if any one of “No” in the increase / decrease operation availability determination table in FIG. 2 is matched, it is determined that the increase / decrease operation cannot be connected in the current blunt condition, and the operator is notified to that effect. While notifying, the increase / decrease operation is canceled and the abnormality adjustment (recovery) operation is performed. On the other hand, if the increase / decrease operation is not being performed, it is activated at the time when the abnormality in purity is detected. That is, if the increase / decrease operation is in progress, it is determined whether the increase / decrease operation is continued using the increase / decrease operation availability determination table of FIG.
Current flow rate (raw material air amount, product oxygen amount, product nitrogen amount, crude argon amount), purity (product oxygen purity, product nitrogen purity, crude argon oxygen concentration), liquid oxygen at the bottom of the upper column Process data such as the liquid level (level), the valve opening of the valve that regulates the flow rate of liquid nitrogen (reflux liquid) from the lower tower to the upper tower, and the rule format of "state of if data then operation" as described above. In the expressed knowledge base, search the knowledge base for a rule that matches the “if data state”,
Perform the following adjustment operation while changing the setting of the operation end and the operation amount defined in “then operation”. Determine whether the adjustment operation is necessary according to the degree of purity abnormality. Adjustment is unnecessary.For example, although it is slightly lower than the lower limit of the stable region for quality control of oxygen purity,
It is heading for recovery in the course of time. In other words, if it is determined that it is likely to return to the stable region in a while, only monitoring is maintained without any adjustment operation, while if there is no sign of returning to the stable region and it is determined that the adjustment operation is necessary. Proceed to the next.

When it is determined that the adjusting operation is necessary, the operation for recovering the abnormality is performed.

 An example of the knowledge base in this case is shown below.

Rule 3: Operation when O ₂ purity rises IF O ₂ Purity does not return O ₂ Purity does not fall THEN O ₂ amount is increased by 1 step In this example, oxygen purity is out of the stable region and tends to improve.
This means that at the time of O ₂ purity increased, "not if O ₂ purity return" of Rule 3 (ie, oxygen purity that does not contain a stable area) "not if O ₂ purity descent" and the condition items that (ie, the current oxygen purity Is not lower than the oxygen purity at the time of the previous data collection), and the rule 3 "Increases the amount of then O ₂ by 1 step" (that is, increases the amount of oxygen generated by 1 step by Δstep ₂₎ . The added value is passed to the measurement control device via the control output unit as the product oxygen generation amount.

When the abnormality is recovered, the process is terminated and the operator is notified of that fact. After performing the operation for abnormal recovery,
The time K (interval time K until the recovery judgment after the operation) is set to determine whether or not the abnormality is recovered, and the operation and the determination are performed after K minutes in the esquispart system start cycle of M minutes.

The interval time K is larger than M (a multiple of M), and the expert system 14 is started in the start cycle M as long as it is abnormal (outside the stable region). Further, like the waiting time N, the interval time K and the starting cycle M are set.
The same CR by switching the operation monitoring screen 4
The contents can be changed interactively on T.

〔The invention's effect〕

According to this invention, the following effects can be expected.

(I) Not only the operation (work) is standardized to prevent erroneous operation, but also the product generation amount adjustment (increase / decrease operation) is possible without being influenced by the degree of skill of driving experience.

(Ii) Labor saving, that is, product oxygen purity, product nitrogen purity, oxygen concentration in crude argon, etc., which was conventionally performed by an operator, and whether the amount of product oxygen generated can be increased or decreased, whether the amount of product nitrogen generated can be increased or decreased, crude argon A large amount of labor can be saved because complicated and advanced judgments such as whether or not the amount generated can be increased or decreased, and the simultaneous increase and decrease operations of product oxygen, product nitrogen, and crude argon, which have been performed with great care, have been performed. Become.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing an increase / decrease operation propriety determination table, and FIG. 3 is a graph for explaining a raw material air amount accompanying a change in product oxygen generation amount, FIG. 4 is a graph for explaining the valve opening degree of the reflux liquid control valve corresponding to the change of the raw material air amount, and FIG. 5 is a block diagram showing the outline of the oxygen plant. Explanation of symbols 1 ... Calculation system 1, 2 ... Calculation control device, 3 ... Oxygen plant, 4 ... CRT, 5 ... Printer, 11 ... Man-machine interface, 12 ... Increase / decrease operation availability determination table, 13 …… Constant file, 14 …… Expert system (increase / decrease operation, adjustment operation), 15 …… Input processing unit, 16 ……
Control output section.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keitoshi Tashiro 1-1-1, Edamitsu, Yawatahigashi-ku, Kitakyushu City, Fukuoka Prefecture Nippon Steel & Co., Ltd. Akisha Yahata Works (72) Inventor Nobuhiko Ando Kawasaki, Kanagawa Prefecture No. 1-1 Tanabe Nitta, Kawasaki-ku, Fuji Electric Co., Ltd. (72) Inventor Ken Terasaki 1-1, Tanabe-Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa Fuji Electric Co., Ltd. (56) Reference Japanese Patent Laid-Open No. 62-238977 (JP, A) JP-B 57-42830 (JP, B2)

Claims (1)

(57) [Claims] 1. An air liquefaction separation apparatus that manufactures oxygen, nitrogen, etc. as a product from air as a raw material and supplies the product to the demand side, even though the production amount of the product required from the demand side fluctuates irregularly. A method of automatically operating an air liquefaction separation device for automatically operating the liquefaction separation device in accordance therewith, when the demand side makes an irregular increase / decrease request for the amount of a specific product, the request is met. That is, the increase / decrease operation propriety determination table for determining whether or not it is possible from the current state of operation of the air liquefaction separation device, and based on the operation experience of the air liquefaction separation device, the increase / decrease amount of the product manufacturing required from the demand side Relatedly, whether or not the raw material supply amount is appropriate is used as a variable of the antecedent part (if part), and the selection of the raw material supply-related operating end to deal with it and the set operating amount of the operating end are used as the consequent part. As a variable in (then part) Based on the first knowledge base consisting of defined inference rules and the operating experience of the air liquefaction separation device, the data of abnormal product quality that may occur during the operation of the liquefaction separation device is used as the antecedent part (if part). ) Variable, and a second knowledge base made up of inference rules set as variables in the consequent part (then part), and the adjustment operation for quality recovery corresponding thereto is provided. When it is determined in the table that the increase / decrease operation is possible, the optimum operation corresponding to whether or not the raw material supply amount is appropriate in relation to the requested increase / decrease amount is then referred to by referring to the first knowledge base. When the product quality abnormality is detected during the operation of the air liquefaction separation device by determining the end and the manipulated variable, and by referring to the second knowledge base from the data indicating the quality abnormality. , Its quality abnormal times An automatic operation method of an air liquefaction separation device, characterized in that an adjusting operation for restoring is determined and executed.